Environmental stability control of the intensity of squall lines under low-level shear conditions

• Published in: Journal of Geophysical Research: Atmospheres 2007-12, Vol.112 (D24), p.n/a
• Main Author: Takemi, Tetsuya
• Format: Article
• Language: English
• Subjects: cloud modeling; convection dynamics; Earth sciences; Earth, ocean, space; Evolution; Exact sciences and technology; Lapse rate; Mesoscale convective system; Potential energy; Shear; Simulation; Squalls; Stability; Static stability
• ISSN: 0148-0227; 2169-897X; 2156-2202; 2169-8996
• DOI: 10.1029/2007JD008793

The environment for the development and evolution of linearly organized convective systems, i.e., squall lines is diverse for their existence in various climate regions. Understanding the behavior of squall lines under various environmental conditions is required for diagnosing and forecasting the development and intensity of the convective systems. The present study investigates the effects of environmental static stability on the squall‐line intensity by conducting a systematic series of idealized cloud‐resolving simulations of squall lines that develop in line‐perpendicular, low‐level westerly shear. Changing the temperature lapse rate with convective available potential energy (CAPE) being unchanged, we showed that the environmental stability in a convectively unstable layer well describes the intensity of the simulated squall lines. A less stable stability is favorable for generating stronger convective systems. The amount of CAPE does not account for the difference in the squall‐line intensity in different temperature environments. An environment with a less static stability leads to the development of stronger cold pool, which will strongly controls the scale and strength of convective updrafts, the intensity of tropospheric overturning, and thus the organization and intensity of squall lines. The CAPE value can only be a good measure for diagnosing the development and intensity of the convective systems so long as the environmental static stability is identical. The static stability is a controlling parameter in determining the intensity of squall lines.